Tilt Motor Killer

[mainexile]

I just bought a 78 Grady White with a Mercruiser 470 stern drive. The previous owner cautioned me that when the engine in running if you try to raise or lower the stern drive (three-button control) the engine dies. I'm going to check for obvious paths to ground, but I was hoping that someone out there has had a similar problem and can point me in the right direction.
Thanks in advance.

 

[HT32BSX115]

Re: Tilt Motor Killer

The pump motor does draw a lot of current. If you have (a) poor ground(s) it could cause that problem.

More likely, the trim pump is getting it's DC A+ power from the same point as the rest of the engine and you're getting a severe voltage drop due to corrosion or a loose/poor connection.

It also sounds like your alternator is not putting out much power at idle.

That's a whole separate issue.

You might want to check you alternator output after you carefully clean and check all the battery connections (plus & minus) also check all the crimped power connections too. They may be corroded enough to cause the same problem. I always solder all my crimped connections when possible. (you can usually only do that on new un-corroded connections)


Cheers,


Rick

 

[mainexile]

Re: Tilt Motor Killer

Rick,

Thanks for the tips. I'll check all the connections and repair accordingly. Just one sticking point: if the alternator were not putting out properly at idle, wouldn't that problem disappear as engoine revs increase? Prior owner says that even at cruising speed if he tried to adjust trim, the engine died. Is it possible that I have a bad winding in the tilt motor? Any idea what sort of reading I should get when checking resistance from tilt motor positive to ground?

Thanks,
Steve

 

[wire2]

Re: Tilt Motor Killer

A Gen 2 trim pump is .2Ω for up or down.
So it will draw ~60 A at 12 volts.
Does the trim kill your gauges too?

 

[mainexile]

Re: Tilt Motor Killer

Wire2,

Previous owner put a switch on the dash that completes the ground path to the trim motor. So as soon as I throw the switch the engine dies. I didn't notice if the other guages were affected. Where are you going with this troubleshooting path?

Thanks,
Steve

 

[wire2]

Re: Tilt Motor Killer

The negative for the pump comes from your dash wiring?
I'm surprised your pump even works. That's a long way for the power to travel, (batt to dash & back to pump) unless the wire is #10 or larger.

Any idea why the previous owner did that?

Have a look at the trim wiring diagram in a manual. It will show the negative coming directly from the batt or block, the positive from the batt to the the solenoids supply, and the +12 V *control only* from the helm to the solenoids.

 

[Wotam]

Re: Tilt Motor Killer

>"Any idea why the previous owner did that?"

I've seen 'safety switches' installed to protect the outdrive models that would self-destruct if run in a trim-up position... if you open the switch it prevents accidental trim operation.

 

[HT32BSX115]

Re: Tilt Motor Killer

Sounds like more of a wiring error and/or a ground loop problem.

The length of wire is not a problem since the switches only control the relays mounted on the trim pump bracket. The current requirements of the relays are small compared to the motor current.

The switch on the dash probably completes the ground to the relays. Not the motor. If it does anything else you need to rewire it. The heavy (#10 or larger) wires plus and negative should be going directly to the battery.

You should have 2 relays (that will probably look like starter solenoids) that actually turn the motor on and off in each direction. The (small) wires from the relays should be the ones going to the dash mounted switches.

I can't point you to an online manual so it might be a good idea to get yourself a Seloc or Clymer manual for a typical wiring diagram.

More than likely someone has got the A+ wire for the engine harness going to one of the trim relays. (If you don't find a ground problem or severely corroded connection)

Does it kill the engine regardless of which way you try to move the trim? Or only one way? (up or down)


Either way you need to isolate the trim system. It should operate separate
from the main key switch. I.E. you should be able to operate the trim/tilt even if the engine ignition is off. (you can wire it to only operate when the ign key is on but it's not required)

 

[wire2]

Re: Tilt Motor Killer

Mainexile, at this point you need to establish;
does your negative for the pump come from the dash switch, (as you stated), or is it only the common to the solenoids.

If it's the latter, the black motor lead will be removed from the solenoid bracket and probably go to the block. But that wouldn't kill the engine.

 

[mainexile]

Re: Tilt Motor Killer

All,

Thank you for your help and insight. I have several things to check when I get home today, and I'll probably post again tonight after I tear the rest of my hair out. BTW HT32BSX115, the engine dies as soon as I flip the switch - I don't have to hit either the "out" or "in" buttons. Thanks again.

Steve

 

[HT32BSX115]

Re: Tilt Motor Killer

Steve,

You may have a wiring error or a defective switch in the tilt and/or main A+ (12v DC) circuit.

I haven't looked at an older Mercruiser wiring diagram in years.

My old one (a 66 Mark Twain) had a separate tilt (power) switch that was a key. If I remember correctly it did not have the capability to trim the engine while underway. I don't remember which year Merc went to a trim system that you could use while under way (anyone?) But I seem to remember some sort of lockout that would kill the engine if the if it was tllted and you turned the trim key off or on or something.




You need to find a wiring diagram to verify the wiring is correct before you try to trouble shoot. It's really hard to troubleshoot without knowing if the thing is wired correctly and/or how it's supposed to be wired in the first place!!

 

[mainexile]

Re: Tilt Motor Killer

The plot thickens... I got the online manual from Seloc and compared the wiring diagrams they have to what's on the boat. Someone really went experimental with this boat's wiring. First, the Trim Sender and Trim Limit switches are nowhere to be found. Apparently, a bell housing replacement was done sometime in the past, and the switches were removed and not replaced. The wires were cut both inside and outside the hull, and the other tilt circuit wiring was replaced without regard to color coding or proper routing. Tonight I'll try to re-route the wiring according to the diagram in Seloc, but I'll have to splice the wires where the tilt sending unit and tilt limit switch are supposed to be. Does anyone see any problem in doing this - other than the upper limit safety factor?

Thanks,
Steve